1. Field of Invention
The present invention relates to an actuator used in an 3 airbag type restraining device or the like.
2. Description of Related Art
As an occupant restraining device or a pedestrian protection device of a vehicle, there are, in addition to an airbag type restraining device, a device for lifting up the hood of a vehicle in order to protect a pedestrian and a device for retracting the steering wheel (shaft/column), and a pyrotechnic actuator is used in such devices.
There is a known actuator in which a pin (piston) is pushed out or retracted upon activation, and, in either case, it is necessary to fix the piston before activation so that it does not move.
In an actuator combined with the above-mentioned restraining device, even after driving the piston, the piston needs to be prevented from returning to its initial position, thus it is preferred, in terms of size and weight reduction of the entire device, that the structure for inhibiting the movement of the piston before and after the activation be simple.
US-B1 No. 6,675,692 relates to a pyrotechnic actuator. As shown in FIG. 1, there is disclosed an actuator in which a piston 2 is slidably disposed within a housing 1 and is driven by a detonator 3. An oblong cavity 2b is formed on the piston 2, and a projection 9 is caused to pass therethrough. A lock (locking element) 8 is disposed so as to surround the projection 9. When a free end 8a abuts on the projection 9 before activation, the piston is inhibited from moving. In FIG. 2, an object corresponding to the lock 8 shown in FIG. 1 is formed in plurality.
In FIG. 7, two studs 2z that are attached to the piston 2 are bent inward by at least a certain amount of force and pass through the piston 2 with respect to the projection. There is disclosed in the 11th through 17th lines of Column 5 that the piston 2 is fixed by the studs 2z before and after activation.
In the actuator of EP-B1 No. 1162333, a piston is disposed within a cylinder and a piston fixing member 13 locks a piston 2 prior to activation (upper left of the drawing). The fixing member 13 is in the form of a washer, and by fitting an inner peripheral portion thereof into an annular groove 12 formed on the piston 2, the piston is inhibited from moving before activation.